This invention relates to traffic crash attenuation and cushion systems. More particularly, the present invention relates to box-beam guardrails and terminals. Even more specifically, the present invention relates to an improved splice mechanism for connecting two stages of a box-beam bursting energy absorbing terminal, sometimes referred to as a BEAT application. A full discussion of this bursting energy absorption technology is found in U.S. Pat. Nos. 6,457,570 and 6,308,809, which are incorporated herein by reference for all purposes. It should be understood that the present invention may be used with any box-beam barrier system or terminal.
Presently, the standard splice mechanism (FIG. 1) for a box-beam guardrail system consists of two plates (A and B) bolted to the inside of the bottom and top of the separate box-beam rails (C and D). FIG. 1 illustrates such prior art splice mechanism. This splice design is not suitable for use with BEAT applications. In order for the bursting process to continue through a splice, it is necessary to shear off the splice bolts and release the splice plates in advance of the mandrel. The energy and the associated force level required to shear off all eight splice bolts E simultaneously is too high for this design to be a viable alternative.
FIG. 2 illustrates an early design of a splice mechanism for use with BEAT applications. The splice mechanism consists of two angles F and F′ welded 50 mm (2 in.) from the downstream end G of the upstream tube H, one on top F and one on the bottom F′. The angles are 63.5×63.5×6.4 mm (2.5×2.5×¼ in.) in dimension and reinforced with gusset plates. Two special splice plates J and J′ were used to connect the upstream tube H and the downstream tube K. The splice plates are fabricated from 13 mm (½ in.) A36 steel plates and welded together to form a L-shape and reinforced with gusset plates. The overall dimensions of the splice plates are 406 mm (16 in.) long, 102 mm (4 in.) wide, and 63.5 mm (2.5 in.) high. The longer legs L and L′ of the splice plates are bolted to the upstream end M of the downstream tube K with two 16-mm (⅝-in.) diameter grade 5 bolts each, again one on top and one on the bottom. The shorter legs N and N′ of the splice plates on the upstream end are then bolted to the angles on the upstream tube, also with 16-mm (⅝-in.) diameter grade 5 bolts.
This initial splice mechanism requires the mandrel to shear off only two bolts at one time, thus greatly reducing the energy and associated force level. Also, the splice plates are outside of the tubes and do not interfere with the mandrel. However, the moment capacity of this splice mechanism is limited by the bolts connecting the splice plates to the angles, rendering the BEAT terminal design somewhat sensitive to redirectional type of impacts.
The present invention maintains the advantages of the early design, but provides a greater moment capacity of the splice and improving the performance of the barrier or crash system for redirectional types of impacts.